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Papers by Leandro D'Orazio

Research paper thumbnail of Adaptive Minimum Conditional Bit-Error-Rate Linear Multiuser Detection for STBC-MC-CDMA Systems Transmitting over Mobile Radio Channels

Lecture Notes in Computer Science, 2010

ABSTRACT This paper proposes an adaptive Minimum Conditional Bit-Error-Rate (MCBER) Multi-User De... more ABSTRACT This paper proposes an adaptive Minimum Conditional Bit-Error-Rate (MCBER) Multi-User Detector (MUD) for a Space-Time Block Coded Multi-Carrier Code Division Multiple Access (STBC MC-CDMA) system that is based on Least-Mean-Square (LMS) optimization algorithm. Theoretical basics and simulation results have been presented and discussed for the proposed detector. Results shown in terms of BER evidenced that the MCBER detector outperforms the adaptive LMS-based implementation of MMSE MUD and also the ideal MMSE MUD exploiting the perfect knowledge of channel state-information. The moderate computational effort and the reduced sensitivity to parameterization seem to represent other relevant strengths of the proposed approach.

Research paper thumbnail of MMSE Multi-User Detection with GA-Assisted Channel Estimation for STBC MC-CDMA Mobile Communication Systems

2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications, 2008

In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase system capac... more In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase system capacity over frequency-selective wireless channels. The key feature of MIMO MC-CDMA is the capability of exploiting diversity jointly in time, frequency and space domains. In particular, Alamouti's coding scheme has been proposed as a very simple and mathematically elegant tool in order to implement space-time block coding. The main problem to be addressed is to effectively recombine diversity in order to achieve the best performances in the presence of multi-user interference. In this paper, we are proposing a low-complexity linear multi-user receiver based on the MMSE criterion supported by a Genetic-Algorithm (GA)assisted MMSE channel estimation. Numerical results show performances very close to MMSE MUD exploiting ideal knowledge of channel state information, thus confirming the near-optimal behavior of genetic algorithms in signal detection and equalization.

Research paper thumbnail of An Adaptive Minimum-BER Approach for Multi-User Detection in STBC-MIMO MC-CDMA Systems

IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference, 2007

Abstract In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase sys... more Abstract In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase system capacity over frequency-selective wireless channels. The key feature of MIMO MC-CDMA is the capability of exploiting diversity jointly in time, frequency and in ...

Research paper thumbnail of A Genetic Algorithm-Assisted Semi-Adaptive MMSE Multi-User Detection for MC-CDMA Mobile Communication Systems

2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006

In this work, a novel minimum-mean squared-error (MMSE) multi-user detector is proposed for MC-CD... more In this work, a novel minimum-mean squared-error (MMSE) multi-user detector is proposed for MC-CDMA transmission systems working over mobile radio channels characterized by time-varying multipath fading. The proposed MUD algorithm is based on a genetic algorithm (GA)-assisted per-carrier MMSE criterion. The GA block works in two successive steps: a training-aided step aimed at computing the optimal receiver weights using a

Research paper thumbnail of Situation-aware radio resource management for multi-rate MC-CDMA wireless networks targeted at multimedia data exchanges in local areas

Proceedings of the 2nd international conference on Mobile multimedia communications - MobiMedia '06, 2006

Research paper thumbnail of Genetic-Algorithm-Assisted Maximum-Likelihood Detection of OFDM Symbols in the Presence of Nonlinear Distortions

IEEE Transactions on Communications, 2000

In this letter 1 , the use of Genetic Algorithms (GAs) has been investigated in order to implemen... more In this letter 1 , the use of Genetic Algorithms (GAs) has been investigated in order to implement a computationally tractable Multi-User Detection (MUD) for synchronous multi-rate Multi-Carrier-Code-Division-Multiple-Access (MR MC-CDMA) systems. It is known that MC-CDMA performances can be seriously limited by multi-user interference. This is particularly true in the case of multi-rate systems where some users could exploit a reduced diversity against multipath channel distortions. The use of Genetic Algorithms (GAs) is therefore proposed as a sub-optimal solution to the MUD problem in a multi-rate Variable-Spreading-Length (VSL) MC-CDMA downlink transmission. A set of selected numerical experiments have been reported and discussed in order to assess the capability of the proposed GA-based approach. The reported results, obtained with an affordable computational burden, have shown a near-optimum behavior of the proposed GA-based MUD.

Research paper thumbnail of Genetic algorithm-based MMSE receiver for MC-CDMA systems transmitting over time-varying mobile channels

Electronics Letters, 2007

In this letter 1 , a novel multi-user detector, based on a Genetic Algorithm-assisted per-carrier... more In this letter 1 , a novel multi-user detector, based on a Genetic Algorithm-assisted per-carrier MMSE criterion, is proposed for MC-CDMA systems transmitting over time-varying multipath fading channels. The analyzed multi-user detector outperforms state-of-the-art adaptive receivers based on deterministic gradient algorithms, particularly for an increasing number of users. Introduction -Despite their intrinsic sub-optimality, multi-user detection (MUD) algorithms based on Minimum-Mean-Squared Error (MMSE) criterion are often preferred in practical applications of Multi Carrier-CDMA (MC-CDMA) due to their reduced computational load and because they can easily support adaptive implementations. In [1] and [2] different MMSE-MUD adaptive receivers for MC-CDMA systems are shown. They are based on Least-Mean-Square (LMS) [1], Recursive-Least-Squared (RLS) [1], and Normalized-Least-Mean-Square (NLMS) [2] optimization algorithms. All these approaches rely on the concept of deterministic

Research paper thumbnail of Is There Light at the Ends of the Tunnel? Wireless Sensor Networks for Adaptive Lighting in Road Tunnels

Existing deployments of wireless sensor networks (WSNs) are often conceived as stand-alone monito... more Existing deployments of wireless sensor networks (WSNs) are often conceived as stand-alone monitoring tools. In this paper, we report instead on a deployment where the WSN is a key component of a closed-loop control system for adaptive lighting in operational road tunnels. WSN nodes along the tunnel walls report light readings to a control station, which closes the loop by setting the intensity of lamps to match a legislated curve. The ability to match dynamically the lighting levels to the actual environmental conditions improves the tunnel safety and reduces its power consumption.

Research paper thumbnail of Adaptive Minimum Conditional Bit-Error-Rate Linear Multiuser Detection for STBC-MC-CDMA Systems Transmitting over Mobile Radio Channels

Lecture Notes in Computer Science, 2010

ABSTRACT This paper proposes an adaptive Minimum Conditional Bit-Error-Rate (MCBER) Multi-User De... more ABSTRACT This paper proposes an adaptive Minimum Conditional Bit-Error-Rate (MCBER) Multi-User Detector (MUD) for a Space-Time Block Coded Multi-Carrier Code Division Multiple Access (STBC MC-CDMA) system that is based on Least-Mean-Square (LMS) optimization algorithm. Theoretical basics and simulation results have been presented and discussed for the proposed detector. Results shown in terms of BER evidenced that the MCBER detector outperforms the adaptive LMS-based implementation of MMSE MUD and also the ideal MMSE MUD exploiting the perfect knowledge of channel state-information. The moderate computational effort and the reduced sensitivity to parameterization seem to represent other relevant strengths of the proposed approach.

Research paper thumbnail of MMSE Multi-User Detection with GA-Assisted Channel Estimation for STBC MC-CDMA Mobile Communication Systems

2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications, 2008

In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase system capac... more In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase system capacity over frequency-selective wireless channels. The key feature of MIMO MC-CDMA is the capability of exploiting diversity jointly in time, frequency and space domains. In particular, Alamouti's coding scheme has been proposed as a very simple and mathematically elegant tool in order to implement space-time block coding. The main problem to be addressed is to effectively recombine diversity in order to achieve the best performances in the presence of multi-user interference. In this paper, we are proposing a low-complexity linear multi-user receiver based on the MMSE criterion supported by a Genetic-Algorithm (GA)assisted MMSE channel estimation. Numerical results show performances very close to MMSE MUD exploiting ideal knowledge of channel state information, thus confirming the near-optimal behavior of genetic algorithms in signal detection and equalization.

Research paper thumbnail of An Adaptive Minimum-BER Approach for Multi-User Detection in STBC-MIMO MC-CDMA Systems

IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference, 2007

Abstract In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase sys... more Abstract In the recent years, MIMO MC-CDMA techniques have been proposed in order to increase system capacity over frequency-selective wireless channels. The key feature of MIMO MC-CDMA is the capability of exploiting diversity jointly in time, frequency and in ...

Research paper thumbnail of A Genetic Algorithm-Assisted Semi-Adaptive MMSE Multi-User Detection for MC-CDMA Mobile Communication Systems

2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006

In this work, a novel minimum-mean squared-error (MMSE) multi-user detector is proposed for MC-CD... more In this work, a novel minimum-mean squared-error (MMSE) multi-user detector is proposed for MC-CDMA transmission systems working over mobile radio channels characterized by time-varying multipath fading. The proposed MUD algorithm is based on a genetic algorithm (GA)-assisted per-carrier MMSE criterion. The GA block works in two successive steps: a training-aided step aimed at computing the optimal receiver weights using a

Research paper thumbnail of Situation-aware radio resource management for multi-rate MC-CDMA wireless networks targeted at multimedia data exchanges in local areas

Proceedings of the 2nd international conference on Mobile multimedia communications - MobiMedia '06, 2006

Research paper thumbnail of Genetic-Algorithm-Assisted Maximum-Likelihood Detection of OFDM Symbols in the Presence of Nonlinear Distortions

IEEE Transactions on Communications, 2000

In this letter 1 , the use of Genetic Algorithms (GAs) has been investigated in order to implemen... more In this letter 1 , the use of Genetic Algorithms (GAs) has been investigated in order to implement a computationally tractable Multi-User Detection (MUD) for synchronous multi-rate Multi-Carrier-Code-Division-Multiple-Access (MR MC-CDMA) systems. It is known that MC-CDMA performances can be seriously limited by multi-user interference. This is particularly true in the case of multi-rate systems where some users could exploit a reduced diversity against multipath channel distortions. The use of Genetic Algorithms (GAs) is therefore proposed as a sub-optimal solution to the MUD problem in a multi-rate Variable-Spreading-Length (VSL) MC-CDMA downlink transmission. A set of selected numerical experiments have been reported and discussed in order to assess the capability of the proposed GA-based approach. The reported results, obtained with an affordable computational burden, have shown a near-optimum behavior of the proposed GA-based MUD.

Research paper thumbnail of Genetic algorithm-based MMSE receiver for MC-CDMA systems transmitting over time-varying mobile channels

Electronics Letters, 2007

In this letter 1 , a novel multi-user detector, based on a Genetic Algorithm-assisted per-carrier... more In this letter 1 , a novel multi-user detector, based on a Genetic Algorithm-assisted per-carrier MMSE criterion, is proposed for MC-CDMA systems transmitting over time-varying multipath fading channels. The analyzed multi-user detector outperforms state-of-the-art adaptive receivers based on deterministic gradient algorithms, particularly for an increasing number of users. Introduction -Despite their intrinsic sub-optimality, multi-user detection (MUD) algorithms based on Minimum-Mean-Squared Error (MMSE) criterion are often preferred in practical applications of Multi Carrier-CDMA (MC-CDMA) due to their reduced computational load and because they can easily support adaptive implementations. In [1] and [2] different MMSE-MUD adaptive receivers for MC-CDMA systems are shown. They are based on Least-Mean-Square (LMS) [1], Recursive-Least-Squared (RLS) [1], and Normalized-Least-Mean-Square (NLMS) [2] optimization algorithms. All these approaches rely on the concept of deterministic

Research paper thumbnail of Is There Light at the Ends of the Tunnel? Wireless Sensor Networks for Adaptive Lighting in Road Tunnels

Existing deployments of wireless sensor networks (WSNs) are often conceived as stand-alone monito... more Existing deployments of wireless sensor networks (WSNs) are often conceived as stand-alone monitoring tools. In this paper, we report instead on a deployment where the WSN is a key component of a closed-loop control system for adaptive lighting in operational road tunnels. WSN nodes along the tunnel walls report light readings to a control station, which closes the loop by setting the intensity of lamps to match a legislated curve. The ability to match dynamically the lighting levels to the actual environmental conditions improves the tunnel safety and reduces its power consumption.